Calculator
Formula used
How to use this calculator
- Enter your floor area and expected design life.
- Add major material quantities from takeoffs or estimates.
- Enter electricity and fuel values as annual totals or per-area.
- Adjust emission factors if you have verified local data.
- Click Calculate footprint to see totals and intensities.
- Use Download CSV for spreadsheets and audits.
- Use Download PDF to share a one-page summary.
Example data table
| Scenario | Area (m²) | Life (yrs) | Concrete (m³) | Steel (t) | Electricity (kWh/yr) | Total (tCO2e) | Intensity (tCO2e/m²) |
|---|---|---|---|---|---|---|---|
| Mid-rise office | 1,500 | 50 | 900 | 120 | 180,000 | ~4,980 | ~3.32 |
| Efficient retrofit | 1,500 | 35 | 220 | 35 | 95,000 | ~1,870 | ~1.25 |
| High-glazing design | 1,500 | 50 | 900 | 120 | 230,000 | ~6,080 | ~4.05 |
Embodied carbon: material quantities drive early decisions
Embodied emissions come from manufacturing and delivering building products. In concept stages, concrete and steel often dominate because their mass is high and their factors are material intensive. Use quantity takeoffs from drawings, then refine with supplier data. If two designs share the same floor area, small changes in structure can shift embodied totals quickly and materially. Include substructure, envelope, and core framing in quantities; omitting foundations or facade framing can understate embodied impacts. As design develops, add reinforcement, finishes, and major MEP materials to reduce bias.
Operational carbon: energy compounds across design life
Operational emissions scale with annual energy use and the chosen design life. Envelope performance, HVAC efficiency, controls, and occupancy schedules all influence kWh per year. Using the default factor of 0.45 kgCO2e/kWh, cutting electricity by 30,000 kWh/yr avoids about 675 tCO2e over 50 years. This makes efficiency upgrades easier to compare against material changes.
Emission factors: replace defaults with verified local sources
Emission factors are the largest uncertainty lever in early estimates. Update grid electricity with your regional average or contract-specific factor, and use Environmental Product Declarations for materials whenever available. Keep units consistent: concrete uses kgCO2e per m³, steel uses kgCO2e per tonne, and bricks use kgCO2e per 1,000 units. Document every factor so comparisons remain transparent.
Water and waste: small yearly loads become meaningful totals
Water and waste can look minor annually, but long lifetimes amplify them. With the default water factor of 0.34 kgCO2e/m³, 5,200 m³/yr contributes about 88.40 tCO2e over 50 years. With the default waste factor of 100 kgCO2e/t, 14 t/yr contributes about 70.00 tCO2e over 50 years. Local treatment and landfill routes can change these values.
Use intensities to compare options fairly across project sizes
Total tCO2e is useful for reporting, but intensities support design tradeoffs. Lifecycle intensity (tCO2e/m²) normalizes for size, while annual intensity (kgCO2e/m²/yr) highlights operational performance. When teams review alternatives, keep the boundary fixed, adjust one variable at a time, and export CSV or PDF so assumptions are carried forward into later design phases.
| Example adjustment | Baseline value | Change | Estimated impact |
|---|---|---|---|
| Electricity reduction (50-year life) | 180,000 kWh/yr | -30,000 kWh/yr | ≈ -675 tCO2e (EF 0.45 kg/kWh) |
| Steel optimization (one-time embodied) | 120 t | -10 t | ≈ -17 tCO2e (EF 1,700 kg/t) |
| Water efficiency (50-year life) | 5,200 m³/yr | -1,000 m³/yr | ≈ -17 tCO2e (EF 0.34 kg/m³) |
FAQs
It estimates embodied materials plus operational energy, water, and waste over the design life. It is intended for early comparisons, not a full compliance life-cycle assessment with transport, refrigerants, or end-of-life modeling.
Concrete and steel often dominate embodied emissions, while electricity and fuel dominate long-term operational emissions. The largest sensitivities usually come from energy intensity assumptions and the emission factors you apply.
Yes. Expand the Advanced emission factors section and replace defaults with verified grid factors and supplier EPD values. Keep unit consistency so your results remain comparable across options.
Start with schematic takeoffs, typical structural ratios, or past-project benchmarks. Update progressively as drawings mature. When comparing options, change only one assumption at a time and document the source of each quantity.
Operational impacts are multiplied by design life in years. A longer life increases total operational emissions unless annual energy is reduced. Use annual intensity to compare operational performance independent of life assumptions.
Total tCO2e is the overall lifecycle estimate. Intensity divides that total by floor area, producing tCO2e per m². Intensity is better for benchmarking and comparing alternative designs of different sizes.
After calculating, use Download CSV for spreadsheets and audit trails, or Download PDF for a one-page snapshot. Keep the notes field updated so exports clearly describe the scenario being reviewed.